Not a bug but something that bugging me - an advance repair system, with spare parts requirement, more break components, number of mechanics needed to repair the vehicle, needed equipment (lift, crane, toolbox...).
In Arma 3 everything is made by magical repair trucks. ACE made it with wheels and tracks only, and everybody says that it's too big and complicate for a single or a small modding team, and has to come from the core itself.

I know how it works in real life, I have the full idea, and would love to make it real.